As soon as I knew that it was a girl I carried inside of me, I began formulating in my mind the ways in which I would explain to her the mysteries of life. When I was a girl, my mother was somewhat squeamish around the subject of where babies come from. My only resource was a book featuring a naked and doughy-looking cartoon couple that my kindergarten classmates passed around with solemn fascination. Although the book had clearly been written for children, it still felt illicit to me. Mostly, I think, because without a parent there we were left to make sense of the information on our own, extrapolating it incorrectly, like a misheard song lyric. (A friend of mine was stunned to find out as an adult that The Beatles did not in fact sing "She's got a chicken to ride ... ")

Armed with this certitude, I vowed that as soon as my oldest, my daughter Mathilda, expressed a desire to know about sex I would tell her, honestly and simply.

"Please just wait until she asks," my husband implored, knowing full well I have a history of jumping the gun. By the time our daughter was in kindergarten herself, we had already read a book together entitled Where Willy Went, a cute and informative story that anthropomorphizes a sperm (Willy), an excellent swimmer who competes with all the other sperm to reach their goal of "Mrs. Brown's egg." (I had originally purchased the book as a birthday present for the 5-year-old son of a friend, thought better of it at the last minute, and got him a stuffed frog instead.) The book deftly handled a big part of the puzzle, but the missing piece of how the sperm is actually delivered was left unrevealed. "Your turn," the book seemed to say. "I'm outta here."

After I assured him that I wasn't about to download Dan Savage's Savage Lovecast for our 5-year-old, I mulled over my approach. Do I buy another book to read together or show her a movie? Do I wait until she happens to encounter dogs "stuck together," as I had in the suburban neighborhood where I lived as a young girl? ("Why are they stuck?" we kids asked. "Ha ha ha," the adults answered nervously as they turned the garden hose on them. Yet another mystery that I would have to puzzle out on my own.)

When my daughter eventually did ask, it was earlier than I had anticipated and not at all as I expected. We were in the car after I had picked her up from kindergarten. I was backing out of a parking space when Mathilda asked from the backseat, "So ... I know how the sperm swims to the egg, but how does the sperm actually get in?"

I glanced at her, startled. It is not uncharacteristic for her to ask things at unexpected times -- she has been the master of the non sequitur since she could speak. Still, I was taken off guard.

"Um ... has anyone talked about this at school?" I inquired with hesitation."Nope," she said.

"Do you have any ideas of your own?" I asked, my voice pitching up at the end, covering at least three octaves by the time the sentence was finished.

"Noooo," she answered, mimicking my tone.

I took a deep breath, began driving, and plunged in as if I were jumping off a boat in winter without a wetsuit. For the next ten minutes I explained the act in the simplest, most straightforward way I could muster. Truthfully, I don't remember much of what I said, but I do know that my mouth kept moving and sound kept coming out. Simultaneously in my mind I was having a future conversation with my husband. "She asked! She ASKED!"

Just as we got to the freeway entrance, I finished the muddled explanation, breathless and flustered. I caught her enormous eyes in the rearview mirror.

"So ... was that what you expected?""Nope," she said."Did anyone talk about that at school?""Nope," she said, shaking her little head emphatically.We drove for a moment in silence."Are you surprised?" I finally asked."Nope," she said, automatically. And then she caught herself. "I mean, YES!"

Later that night my husband shook his head. "Did you have to include the part about the penis getting bigger?"

"It was a logic issue," I insisted. Still, at the parents' cocktail party later that week, I felt the need to address each parent individually. "That was me," I confessed. "Whatever you hear from your kids this week, that was me. I'm sorry." All of the parents were remarkably sanguine in regard to my oversharing. Then again, I do live in Southern California.

The whole experience, however, did make me question my previously steadfast belief that transparency is the way to go with my children. And while I'm not running for political office anytime soon, where transparency is (or least should be) a job requirement, parenting is a delicate, nuanced business. What works for one child does not for another.

With this in mind, I temper my parceling out of information based on the temperament of my children. Some things I know my now 10-year-old daughter will never want to hear from me. I have more or less resigned myself to the fact that her need to discover things herself extends to almost every aspect of her life. In contrast, my younger daughter will ask the same question, very often a question that she already knows the answer to, and continue to ask until she hears me tell her. Why am I closing the door? Yes, so the dog doesn't get out. Why do I kiss you? Yes, because I love you. My son, meanwhile, acts, and asks later.

Six months after the premature sex-talk debacle with Mathilda, we went on a hike together, and once again she lobbed a non sequitur at me.

"Guess what, Mommy," she said."What?"

"I know how babies are made." She told me this in the secretive, confiding tone of a housewife sharing a particularly choice tidbit of gossip.

In my mind I thought, "Are you really going to tell me what I told you six months ago?" I was tempted to change the subject, to bring up global warming, the differences between bobcats and mountain lions -- anything but the subject at hand -- but there she was, smiling an irrepressible grin. So instead, I asked.

"Oh? How's that?""Kissing," she said.

And confident in her knowledge she skipped away, scrabbling up the thorny, perilous California mountainside.